In order to speed up enumeration, it would be nice to be able to pass an option into enumerate so that we can filter out any older modification dates.
For example:
var storage = navigator.getDeviceStorage("pictures");
ok(navigator.getDeviceStorage, "Should have getDeviceStorage");
// 836031600 is a long time ago
var cursor = storage[0].enumerate(path, {"since": new Date(836031600)});

> Shouldn't we allow both since and path here?
I thought about it. The current APIs on Device Storage looks like:
DOMDOMRequest function(optional DOMString path)
All of the other APIs on device storage take an optional string. I didn't want enumerate to take this optional string only when it was an attribute inside an options object. This is true for add(), get(), delete(), and enumerate().